Switch devices are used to switch voltages or currents, for example to selectively couple a load to a voltage and/or current source, or to switch signals within a circuit. In some applications, it is desirable to measure a current flowing through the switch device. Some switch devices, also referred to as power switch devices may use transistors as switches and may be designed to switch high currents, for example several Amperes or several tens of Amperes, and/or high voltages, for example several hundred Volts. Measuring high currents may be a challenge for example in view of limiting power dissipation.
Various approaches for such current measurements have been employed. For example, a current measurement circuit, for example including a current mirror, may be integrated together with a semiconductor power switch on a single chip die. In other approaches, a current measurement circuit may be provided outside a package housing a semiconductor switch (for example a measurement resistor or measurement transformer) or may be provided within the package, but outside the chip die. Monolithically integrated approaches in some cases may not have a desired accuracy and/or may not be galvanically isolated from a load current. Approaches outside a package require corresponding space, may have high losses with associated power dissipation in case of resistors or may be comparatively expensive.
In one approach for current measurement, a magnetic field sensor device is provided within the package to measure the load current by sensing a magnetic field generated by the load current. A magnetic field sensor device may be implemented as a bridge circuit, where at least some of the elements forming the bridge circuit are magnetoresistive elements like anisotropic magnetoresistive (AMR) giant magnetoresistive (GMR) or tunneling magnetoresistive (TMR) sensor elements, or may be implemented as Hall sensor.
For generating a sufficient magnetic field to be sensed by the magnetic field sensor device, a conductor where the current is measured needs to have a certain inductivity. On the other hand, such an inductivity may reduce a switching speed to the switch device and increase losses when switching on the switch device. Furthermore, the switching speed may also depend on the load current.